In a gas turbine engine power turbine nozzle control for providing vehicle braking



A. F. M LEAN A ril 9, 1988 l t e e h Ls O RS Tt ww Ch 3 E L2 Z Z O NG IN A GAS TURBINE ENGINE, POWER TURBINE FOR PROVIDING VEHICLE BRAKIN Filed Dec. 30, 1966 F'IG.4

RETARDER PEDAL N S V mm N R EC 1 m W .&T I Mk A 6 MW AY .w w mm 1 IOVK Rm EL T m 3,3 76,702 CONTROL A. F. M LEAN Aprii 9, 1968 IN A GAS TURBINE ENGINE, POWER TURBINE NOZZLE FOR PROVIDING VEHICLE BRAKING 2 Sheets-Sheet 2 Filed Dec. 50, 1966 SE33 mjtomri mm} H A\\ 30% MKPEEEEF w U mmomapwm mm mwmmm flail Unite States Patent 3,376,702 Patented Apr. 9, 1968 H's-M...

ABSTRACT OF THE DISCLOSURE Depression of an operator movable pedal first causes a valve to be opened to supply fluid to move the power turbine nozzles to positions retarding rotation of the power turbine, and, secondly, essentially concurrently, increases the fuel to the engine to'increase the gas flow through the power turbine and thereby increase the braking action.

This invention relates, in general, to a fluid pressure control system. More particularly, it relates to a control for the power turbine of a gas turbine engine that is installed in a motor vehicle.

Motor vehicle gas turbine engines generally provide for a change in the engine output speed not only by controlling the fuel supply, but also by changing the pitch of the power turbine nozzles. The adjustability of the nozzles, therefore, is used as a control for the various acceleration, deceleration and braking phases of operation of the turbine.

From an operators standpoint, the most desirable method of operating the vehicle is to have essentially only a few main controls. To accomplish this, the nozzle actuator system should provide a precise adjustment of the turbine nozzles in accordance with power demand as indicated by the degree of movement of the accelerator pedal so that the engine can be brought up rapidly to and maintained in a particular operating condition, such as, for example, with a constant turbine inlet temperature. Also, the nozzle control system should be capable of automatically decelerating the engine, and indirectly the vehicle speed, when the turbine inlet or exit temperatures rise above a safe level, or the accelerator pedal is released to an idle speed position so that undesirably high turbine inlet temperatures and other conditions will not occur. Additionally, the operator should be able to actuate the power turbine nozzles to an engine braking position when it is desired to retard vehicle motion.

The invention satisfies the above requirements by providing a nozzle actuating system that consists, in general, of a fluid pressure operated servo device for accurately adjusting the positions of the turbine nozzles; a fluid. controlling shuttle mechanism for controlling the move ment of the servo; and accelerator pedal control and nozzle motion feedback mechanism for regulating the movement of the shuttle valve; and a number of auxiliary control means for braking the rotation of the engine output shaft either automatically when the throttle lever is released to its engine idle speed position, or the turbine section temperature rises above a safe operating level, or selectively when desired to retard movement of the vehicle.

A primary object of this invention is to provide a control for the turbine nozzle pitch adjusting mechanism that is selectively activated by the vehicle operator to effect retarding of the vehicle motion when desired.

A further object of the invention is to provide a motor vehicle type gas turbine engine wit-h a vehicle motion retarder pedal cooperating with a fiuid control and the engine fuel control in such a manner that initial move ment of the pedal effects a movement of the power turbine gas inlet nozzles to a position directing the gas against the power turbine blades in a motion retarding direction, and subsequent movement of the pedal opens the fuel control to increase the gas flow and thereby the braking action. I

Other objects, features and advantages of the invention will become apparent upon reference to the succeeding, detailed description thereof, and to the drawings illustrating the preferred embodiment thereof; wherein,-

FIGURE 1 is a side-elevational View of a turbine nozzle actuating system embodying the invention;

FIGURE 2 is an enlarged cross-sectional plan view, with parts broken away and in section, of the nozzle actuating system shown in FIGURE 1;

FIGURE 3 is a schematic cross-sectional view of a turbine nozzle and turbine blade;

FIGURE 4 is a schematic illustration of a control assembly;

FIGURES 5 and 6 are cross-sectional views of details taken on planes indicated by and viewed in the direction of arrows 5-5 and 6-6, respectively, of FIGURE 2; and FIGURE 7 is an enlarged schematic View of the invention shown in FIGURE 2,

FIGURES l and 2 show one view of a turbine nozzle control that embodies the invention. It would be secured as an accessory to the housing (not shown) of a gas turbine engine (also not shown). The details-of the gas turbine engine are not given since they are known and are believed to be unnecessary for an understanding of the invention. Suffice it to say that the engine would have one or more conventional axial flow type compressor and power turbines, and that the stationary powerturbine nozzles indicated schematically at 1 would be posi-v tioned between the usual diffuser section and power turbine rotor blades 2 (FIGURE 3) to control the direction of discharge of combustion product gases to ell'ect the desired rotation of the turbine rotor or rotors.

FIGURE 3 shows, schematically, the cooperation between a typical turbine nozzle 1 and an axial flowturbine blade 2. The range of movement of thenozzle forrotation and acceleration of turbine blade 2 in the direction of arrow 3 is indicated in general by dotted lines 4-and 5. When the nozzle moves between these positions, the gas will discharge against the back side of turbine blade 2 and thus rotate it forwardly.

During the initial accelerating phase of the motor vehicle, the nozzles 1 will be moved clockwise progressively towards the full line position 4 as a function of the position of the vehicle accelerator pedal to provide rotation of the turbine and engine output shaft as called for. On the other hand, if the turbine inlet or exit temperature is excessive, or the vehicle operator releases the accelerator pedal, such as, for example, during vehicle deceleration of engine idle speed operation, or if-theoperator selectively actuates a control to be described, the nozzles 1 will be pivoted progressively backwards toward the dotted line braking position 6 so as to change the direction of discharge of the gases from the nozzles to strike the front portions of the turbine blades to thereby retard rotation of the rotor blades 2 in the forward direction. Retarding the power turbine rotation will, of course, retard the engine output shaft rotation since they normally are interconnected by suitable reduction gearing, not shown.

FIGURE 2, which is essentially to scale, shows the details of the control system. It includes, in general, a combined housing and valve body 8; a servo mechanism 19 that is operatively connected by suitable push-pull type linkage 12 to the turbine nozzles 1; a shuttle valve mechanism 14 that controls the flow of fluid to operate servo mechanism an accelerator pedal rotated throttle valve member 16- for control-ling the movement of shuttle valve mechanism 14; a power feedback mechanism 18 for rearming the shuttle valve mechanism by returning it to a neutral position when the nozzles move to the position selected; an operator-controlled transmission selector control valve 20 for effecting rotation of the nozzles to brake the power turbine when the Vehicle transmission is in neutral; and controls for braking the engine output shaft at times, namely, an engine output shaft speed sensitive valve means 22; a vehicle speed sensitive valve 24, a turbine section temperature sensitive means 26, and an engine braking or vehicle retarding control 27.

More specifically, servo mechanism 10 includes a stepped diameter cylindrical bore 28 closed at one end by a conically-shaped cap 30 that abuts and locates a cylindrical sleeve 32. The sleeve encloses an annular piston 34 having an actuating rod 36 that projects through housing 8 to a connection with linkage means 12. The linkage in this particular case, as best seen in FIGURE 1, rotates a lever 38 that is fixed in a suitable manner to turbine nozzle 1 to rotate it about its pivot point 40 (FIGURE 3). In practice, the nozzles would all rotate as a unit, in a manner similar to that shown in FIGURE 4; that is, the piston rod would rotate a ring gear 42 in mesh With a gear 44 secured to each nozzle.

Piston 34 is reciprocated in opposite directions by alternately admitting fluid under pressure to opposite ends of the bore of sleeve 32 through suitable passages 46 and 48. These latter passages are connected to a pair of annular fluid manifolds 50 and 52 that are controlled by shuttle valve mechanism 14.

The shuttle valve mechanism is mounted in a stepped diameter bore 54 that is closed at opposite ends by caps 56 and 58. The bore has a main drain passage 60 connected to a sump, not shown. The bore also has a sleeve member 61 that slidably and sealingly supports a spool valve 62. The spool valve is of a known type having spaced lands 64 and 66 interconnected by a neck portion 68 to define a fluid annulus 70. The annulus is connected at all times to an annular fluid pressure supply passage 72 that is supplied with fluid under pressure from any suitable source, not shown,-'whenever the engine compressor is driven.

Spool valve 62 is normally positioned in a central or neutral position blocking flow of fluid from passage 72 to either of the servo passages 46 and 48. The shuttle valve is urged towards this position by a pair of centering springs 74 and 76 that are seated against cam followers 78 and 80. The cam followers are slidably mounted within suitable sleeves 82 and 84 non-movably fixed in the valve body.

The bore 54, cap 56, sleeve 82 and left-hand cam follower-78 together define a fluid chamber 86. The chamber is essentially closed except for controlled orifice connection 88 (see FIGURE 5) to main drain passage 60, for a purpose to be described later. Right-hand cam follower 80, together with bore 54, sleeve 61 and cap 58, form a second chamber 90 that is connected at all times to drain passage 60.

Left-hand cam follower 78 abuts against the profiled surface of a cam 92 that is fixed for rotation with the throttle valve member 16. This member projects into fluid chamber 86 and includes a shaft 94 that is rotatably mounted within a sleeve 96 fixed within housing 8. Shaft 94 is connected at its opposite end to a lever 98 that is adapted to be connected to the conventional motor vehicle accelerator pedal linkage (not shown) so that movement of the accelerator pedal will swing lever 98 by a proportionate amount.

The right-hand cam follower 80 abuts against the pro filed surface of a cam 100 that is fixed for rotation with a power feedback control shaft 102. This shaft, at its opposite end, is suitably connected by a lever 104 and 4 push-pull linkage 106 to the radially inner portion of lever 38 (FIGURE 1) that is rotatable with the turbine nozzles 1. This construction transmits the nozzle rotation back through cam 100 to shuttle valve 62 to return it to its neutral position to maintain the piston 34 in the position selected by the position of throttle valve member cam 92. With the construction as thus far described, the valve assembly will provide for accelerating and decelerating positions of nozzles 1 in accordance with the movement.

of the vehicle accelerator pedal and rotation of throttle valve member 16. As stated previously, however, other controls are also desired for preventing excessive turbine section temperatures, and excessive engine output shaft speeds when the transmission is in neutral condition and/or the vehicle accelerator pedal is released to an engine idle speed position.

Consider first the control to aerodynamically brake the power turbine when the turbine inlet or exit temperature rises above a desired value. Left-hand fluid chamber 86 is connected at all times to a fluid conduit 107 that contains a signal fluid pressure supplied by the temperature sensing means or probe 26. This latter means includes a housing 108 having a hollow probe 109 of high expansion material enclosing and confining a stem 110 of low expansion material. Stem 110 is abutted by a needle-like valve member 111 that slides through an aperture 112 connecting two fluid chambers 113 and 114, and is biased against stem' 110 by a spring 115.

Chamber 113 is connected by a line 116 to a source of regulated fluid under pressure, which could be a branch of main supply port 72. Chamber 114 is connected to line 107. Housing 108 also contains a fluid return line 117 having a fixed bleed orifice 118 permitting a pressure build-up in chamber 114 and line 107.

The thermal sensitive probe 109 would be inserted in the turbine section of the engine, either at the gas inlet or exit portions, or both, as desired, so as to sense the changes in gas temperature therein.

In operation, if the turbine gas temperature rises above a safe operating level, the probe outer housing 109 will expand relative to stem 110 and thereby permit spring to move valve 111 to the right to increase the fluid flow between chambers 113 and 115 and line 107. Assuming a correct size of orifice 88 in shuttle valve chamber 86, the increased flow into chamber 86 will cause a pressure build-up suflicient to move cam follower 78 to the right away from throttle member cam 92. This will cause shuttle valve 62 to move to the position shown, or beyond,

to supply fluid through servo line 46; Piston 34 will then be moved to rotate the turbine nozzles 1 towards the open braking position 6. The resultant opening movement of the turbine nozzles, with respect to the gas passage, will decrease the turbine temperature and simultaneously slow down the turbine.

Consider now the control to brake the turbine and 1 thereby indirectly retard creep of the vehicle during en-- gine idle speed operation, when the transmission is engaged for a drive condition. Throttle member shaft 94 1 has a central bore 119 that is open at one end to chamber 86, and has restricted crossbores 120 and 121. of different sizes. The bores 120 and 121 are adapted to cooperate with different size orifices 122 and 123 in sleeve 96 that are connected at all times to annular fluid manifolds 124 t and 125. As best seen in FIGURE 6, the crossbores of shaft 94 are so arranged that when the shaft is rotated by the vehicle accelerator pedal to the engine idle speed position shown in FIGURE 6, the shaft crossbores 120 and i 121 will be aligned with the flow restricting orifices 122 1 and 123. Thus, any fluid under pressure in the manifolds 124 and 125 will have a controlled flow into the central whether both manifold 124 and 125 contain fluid, or just one.

The supply of fluid to manifolds 124 and 125 is controlled by the vehicle s-peed sensitive valve mechanism 24, the transmission selector lever valve 20, and the engine output speed sensitive valve 22. Valve mechanism 24 includes a spool valve 126 slidably mounted within a sleeve fixed in the valve body or housing 8. The spool valve has spaced lands 127 and 128 interconnected by a neck portion 130 defining an annular fluid chamber 132. The valve is biased to the position shown against an adapter plug 134 by a spring 136, the chamber 138 containing the spring being vented to exhaust through a port not shown. The opposite end of the valve is adapted to be moved upwardly by fluid under pressure admitted through a passage 140 from a vehicle output shaft speed sensitive source of fluid under pressure (not shown) that develops a pressure that changes with changes in vehicle speed.

The valve body for valve 126 has annular manifolds 142 and 144. Manifold 142 is connected by ports 146 to the valve bore and by a passage 148 to throttle valve manifold 124. Manifold 144 is connected by a passage 150 to main fluid supply passage 72 and by ports 152 to the valve bore. Manifold 144 is also connected by passage 154 past selector lever control valve 20 to throttle valve manifold 125.

In the position shown, valve 126 connects fluid under pressure from line 150 directly to throttle member manifold 125, when valve 20 is in the position shown. When the vehicle output shaft speed is above a predetermined value, the pressure in line 140 raises valve 126 so that fluid will also flow through passage 148 to the throttle valve manifold 124.

Valve 20 provides the transmission selector lever control of the nozzle position. This valve has a 90 rotation between two positions permitting flow to throttle valve member manifold 125 either from the vehicle speed sensitive value 126 through line 154, or from the engine output shaft speed sensitive valve 22 through a line 156. Valve 20 would be connected to the vehicle transmission selector lever by suitable linkage, not shown. Moving the selector lever to a drive position would move valve 20 to the position shown. Moving the selector lever to a neutral position would rotate the valve 90 counterclockwise to connect the throttle valve manifold 118 to line 156.

The engine output shaft speed sensitive valve mechanism 22 includes a spool valve 158 slidably mounted in the valve body to control flow of fluid under pressure to line 156 from a branch 160 of main supply line 72. The valve is normally biased to the right by a spring 162 to close line 156, and is moved to .the position shown by a signal fluid pressure in a line 164 that increases as a function of the increase in speed of a pump or other suitable member driven by the engine output shaft.

Consider now the control 27 that is actuated at will by the vehicle operator to provide engine braking to retard movement of the vehicle. As seen more clearly in FIGURE 7, the vehicle in which the gas turbine engine is installed would be equipped with what can be called a retarder pedal 170. This pedal would be in addition to the conventional brake and clutch and accelerator pedals.

Pedal 170 is pivotally mounted at one end 172 for an arcuate movement, and has a pivotal connection to a link 174 near its midpoint. Link 174 in turn would be connected by suitable linkage 176 and a pivotally movable lever 178 to the engine fuel control 180. Depression of lever 170 by the foot of the operator would move lever 178 clockwise about pivot 182 to increase the fuel supply to the engine combustion chambers, not shown, in the conventional manner. This would result in an increased gas flow through the turbine section.

The upper portion of retarder pedal 170 is provided with an L-shaped actuating flange 184. In the full line position of pedal 170 shown, flange 184 moves the stem 186 of a micro or other suitable switch 188 upwardly against the bias of a spring 190 to a position opening a 6 set of electrical contacts 192; that is, to a position opening switch 188. Depression of pedal 170 to the dotted line position indicated permits spring 190 to close the switch.

Switch 188 is connected as shown to the windings 194 of a solenoid 196. The solenoid has an armature 198 that also functions as the stem of a fluid flow regulating valve 200. The solenoid is sealingly enclosed in a housing 202 that has a fluid inlet port 204 and an outlet 206. Valve 200 is normally biased by a spring 208 to the position shown closing inlet port 204, and is pulled upwardly when solenoid 196 is energized upon closing of switch 188 after depression of retarder pedal 170.

Any suitable source of electrical energy, not shown, may be used to supply current through the switch to the solenoid. The supply of fluid under pressure for inlet 204 can be provided by any suitable pump, not shown. Preferably, the supply source would be at a constant pressure level.

Fluid outlet 206 is connected by a line 210 (FIGURE 2) directly to throttle chamber 86 so that when valve 200 is raised, the pressure in chamber 86 will increase and move shuttle valve 62 to a position effecting rotation of the turbine nozzles to their full braking positions.

Essentially simultaneous with the closing of switch 188, depression of the retarder pedal 170 will increase the fuel flow to the engine by rotation of lever 178 from its idle speed position shown (FIGURE 7) towards a maximum position. This will increase the compressor r.p.m. and the engine air flow, and thus the gas flow through the power turbine. Since the turbine nozzles are now in the braking positions, the increased gas horsepower will increase the retarding effect on the rotation of the power turbine. Further depression of the retarder pedal, therefore, will progressively increase the braking action.

The over-all operation of the nozzle control is as follows: When the engine is inoperative, the nozzles 1 will be somewhere in the turbine braking range since the accelerator pedal will have been released, and one or more of the controls described'will have increased the pressure in chamber 86 sufliciently to cause the piston 34 to rotate the nozzles to this position. Assume, therefore, that the vehicle is standing still, the vehicle accelerator pedal is released, and the gas turbine engine is idling at a low speed, with the transmission selector lever in neutral, and retarder pedal 170 released. Engine output shaft speed valve 158 will be in a position blocking line 156, vehicle speed valve 126 will be in the position shown, and transmission selector lever valve 20 will be rotated to the left blocking flow from valve 126 through passage 154. Therefore, there will be no flow of fluid into chamber 86 except that due to the turbine temperature control 2 6, and the piston 34 and nozzles 1 will remain in the braking position.

If now the engine output shaft speed should, for some reason, increase above the idle speed setting of valve 22, the increase in pressure of the fluid acting against valve 158 will move it to the left to connect lines and 156 and thus, through selector valve 20 and the bore 119 of throttle valve shalt 94, pressurize chamber 86. This moves cam follower 78 and shuttle valve 62 to the right, admitting fluid from port 72 to servo passage 46. Piston 34 thus is urged to the right to rotate the nozzles 1 towards a greater turbine braking position, which will reduce the engine output shaft speed and close the cycle.

Assume now that the operator moves the transmission selector lever to drive position. This moves valve 20 to the position shown, and connects the fluid in manifold 144 of valve 126 to the throttle valve shaft bore 119 through orifice 123 and port 121. Fluid will then pressurize chamber 86 a predetermined amount sufficient to maintain the engine output shaft braked in substantially the same manner as described above.

If the operator now depresses the accelerator pedal to effect a movement of the vehicle, all communication of fluid to chamber 86, except that from temperature control 26, is immediately cut off, thus permitting the chamber to be drained through the orifice 88 and relieve the pressure build-up against cam follower 78. The progressive or quick depression of the accelerator pedal now rotates throttle shaft 94 and cam 92 to relieve the pressure on cam follower 78 and spring 74 and permit opposite centering spring 76 to move shuttle valve 62 to the left. This opens servo passage 48 to supply port 72, while connecting servo line 46 to drain line 60 through the right end chamber 90. Piston 34 thus moves progressively to the left and rotates nozzles 1 to their closed, turbine accelerating positions and 4. As the nozzles rotate, the feedback exerted through linkage 106, 104 and shaft 102 rotates cam 100 to relieve the force on cam follower 80 and spring 76. The shuttle valve 62 thus begins to move back towards a neutral position under the influence of spring 74. The fluid supply to servo passage 48 thus is progressively cut off and finally terminated when the nozzles 1 have reached the accelerating position corresponding to the degree of depression of the accelerator pedal and rotation of throttle control member cam 92.

It will be clear that if the driver should partially re lease the accelerator pedal, that rotation of cam 92 in the opposite decelerating direction will cause a reverse operation of the shuttle valve mechanism. That is, shuttle valve 62 will be moved to the right to connect supply port 72 and servo passage 46 so that piston 34 will be moved to actuate the nozzles to a lesser accelerating position, depending upon the new position of the accelerator pedal.

If, after the vehicle has been accelerated, the operator should completely release the accelerator pedal to its idle speed position, both orifices 122 and 123 in throttle valve shaft 94 are opened to control passages 148 and 154. If the vehicle speed is above a predetermined value, valve 126 will have been moved upwardly by the speed sensitive fluid pressure in line 140 so that fluid under pressure in line 150 now is supplied through both lines 148 and 154, thereby pressurizing chamber 86 to a high value. This moves cam follower 78 and shuttle valve 62 to the right causing piston 34 to move in a rightward direction to actuate the nozzles 1 to their maximum turbine braking positions.

If, at the same time, the transmission selector valve 20 should be moved to a neutral position (rotated 90 to the left), supply of braking pressure to the throttle member manifold 125 from valve 126 through line 154 would be cut off; however, manifold 125 would now be supplied from line 156, if we assume the engine output shaft speed is above the set value. The engine output shaft would then again be braked. Of course, if the engine output shaft speed is below the set level but the vehicle speed is not, flow through the upper passage 148 alone is still suflicient to rotate the nozzles towards their turbine braking positions when the accelerator pedal is in its engine idle speed condition.

Control of the nozzle position by the turbine gas temperature sensitive probe 26 has already been described, and, therefore, is not repeated.

Alternately, even though the accelerator pedal is released, if more engine braking is desired, retarder pedal 170 can be depressed to move the turbine nozzles to the braking position and concurrently increase the gas flow to progressively increase the braking action. That is, as described previously, closing of switch 188 energizes solenoid 196 to open valve 200 and increase the pressure in throttle chamber 86. This moves shuttle valve 62 to actuate servo piston 34 to move the power turbine nozzles to the full braking position. The increasing fuel supply then increases the gas flow through the power turbine, but it is now acting in a retarding manner on the power turbine and engine output shaft. The vehicle will then be slowed down to the desired level, assuming that the vehicle transmission is not disengaged from the engine.

From the foregoing, therefore, it will be seen that the invention provides a control for a motor vehicle gas tur- 8 bine engine that provides orientation of the turbine inlet nozzles as a function of the position of the vehicle accelerator pedal and the turbine section temperature; and

that it provides engine braking whenever the turbine section temperature is excessive or the accelerator pedal is released to its idle speed position, and the vehicle speed is above a predetermined value, or the transmission selector lever is placed in neutral position and the engine output shaft speed is above a desired value, or whenever the a vehicle operator depresses the retarder pedal.

The invention thus provides many advantages; namely, the turbine nozzles can be positioned accurately to maintain given engine operating conditions; any schedule of nozzle positions can be accommodated by correct profiles of the cams on the throttle member and feedback mechanism; idle and braking positions of the nozzles can be achieved separate from the requirements for maintaining given engine conditions; the servo shuttle valve action achieves fast respon e; the vehicle automatic transmission can be placed in neutral at engine idle speed operation; While the transmission is in neutral or park or start condition, the engine output shaft speed is governed, thereby preventing an overspeed of the engine and maintaining the gear noise level and other men1- bets to an acceptable level and permitting a driving of the accessories, such as air conditioning, from the engine output shaft; the engine will be easier to start, and a smaller starter motor can be used because the transmission can be placed in neutral; a manual transmission can be used with the gas turbine engine; and, the engine will not suifer the large temperature and surge changes associated with changes in accessory power because the accessories can be driven while the transmission is in neutral.

While the invention has been illustrated in its preferred embodiment, it will be clear to those skilled in the art to which the invention pertains that many changes and modifications may be made thereto without departing from the scope of the invention.

Iclaim:

1. In a gas turbine engine having a rotatable power operated means, operably effecting movement of i said power operated means and retarding of the rotation of said power turbine,

control means in said conduit means movable between conduit means opening and closing positions,

and multi-position movable operator controlled means operably connected to said control means such that when moved towards one position said control means is moved to a conduit means opening position to operably effect a retarding of the rotation said power turbine,

said control means including an on off valve movable in said conduit means to control the flow of fluid therethrough, and means operably connecting said operator controlled means and said valve for movement of said valve to permit flow through said conduit means upon movement of said operator controlled means toward said one position,

said last mentionedmeans including selectively activated power actuated means connected to said valve, and

activating means for said power actuated means operably connected to and activated by a predetermined movement of said operator controlled means towards said one position.

2. In a gas turbine engine as described in claim 1,

said operator controlled means comprising a movable pedal,

said activating means being operably engaged by said pedal and rendered inactive thereby, movement of said pedal to a predetermined position activating said activating means.

3. In a gas turbine engine having a rotatable power turbine driven by the products of combustion from said engine, an adjustable power turbine gas inlet nozzle, a power out-put shaft operably driven by said rotatable power turbine, and power operated means movable at times to adjust said nozzle to retard the rotation of said power turbine,

the improvement comprising,

a source of fluid under pressure, conduit means operably connecting said source and said power operated means, operably effecting movement of said power operated means and retarding of the rotation of said power turbine,

first control means in said conduit means movable between conduit means opening and closing positions, fuel control means movable between minimum and maximum fuel flow positions for varying the gas flow through the said engine, and multi-position movable operator controlled means operably connected both to said first control means and said fuel control means such that when moved towards one position said first control means is moved to a conduit means opening position to operably effect a retarding of the rotation of said power turbine and said fuel control means is moved towards said maximum fuel flow position to increase the gas flow through said engine and thereby increase the retarding of rotation of said power turbine.

4. In a gas turbine engine as described in claim 3, said first control means including an on-olf valve movable in said conduit means to control the flow of fluid threrethrough, and means operably connecting said operator controlled means and said valve for movement of said valve to permit flow through said conduit means upon movement of said operator controlled means towards said one position.

5, In a gas turbine engine as described in claim 4,

said last mentioned means including selectively activated power actuated means connected to said valve, and

activating means for said power actuated means operably connected to and activated by a predetermined movement of said operator controlled means towards said one position.

6. In a gas turbine engine as described in claim 5, said operator controlled means comprising a pedal pivotally connected to said fuel control means and operably engaging said activating means.

7. In a gas turbine engine having a power output shaft operably driven by a rotating power turbine, power turbine gas inlet nozzles adjustable to positions guiding the gas flow to said power turbine in directions effecting braking of the rotation of said power turbine and output shaft, a reciprocable fluid pressure actuated servo mechanism connected to said nozzles for moving said nozzles to said positions, a source of fluid under pressure, conduit means connecting said source and mechanism, and shuttle means in said conduit means re- 16 ciprocable to control the flow of fluid to opposite portions of said mechanism,

the improvement comprising,

selectively operable means when operable applying a force to said shuttle means to effect a retarding of the rotation of said power turbine, and operator movable means operably connected to said selectively operable means for rendering operable said selectively operable means to effect a movement of said nozzles to retard the rotation of said power turbine, said selectively operable means including,

a second source of fluid under pressure, other conduit means connecting said second source to said shuttle means to apply an additional force thereon, and a regulating valve in said other conduit means movable between positions to control the flow of fluid from said second source to said shuttle valve.

8. In a gas turbine engine as described in claim 7, said operator movable means comprising a p-ivotally mounted pedal.

9. In a gas turbine engine having a power output shaft operably driven by a rotating power turbine, power turbine gas inlet nozzles adjustable to positions to direct the gas flow to said power turbine in directions eflecting braking of the rotation of said power turbine and output shaft, a reciprocable fluid pressure actuated servo mechanism connected to said nozzle for moving said nozzle to said positions, a source of fluid under pressure, conduit means connecting said source and mechanism, shuttle means in said conduit means reciprocable to control the flow of fluid to opposite portions of said mechanism, and fuel flow control means movable between minimium and maximum fuel flow positions to vary the flow of fuel to and the flow of gas through said engine,

the improvement comprising,

selectively operable means when operable applying a force to said shuttle means to effect a retarding of the rotation of said power turbine, and

operator movable means operably connected both to said selectively operable means and to said fuel control means for rendering operable said selectively operable means and moving said fuel control towards said maximum fuel flow position upon movement of said said movable means,

the rendering operable of said selectively operable means moving said nozzles to retard the rotation of said power turbine, the movement of said fuel control towards said maximum position increasing the gas flow through said nozzles to thereby increase the retarding of rotation of said power turbine.

10. In a gas turbine engine as described in claim 9, said selectively operable means including,

a second source of fluid under pressure,

other conduit means connecting said second source to said shuttle means,

and a regulating valve in said other conduit means movable between positions to control the flow of fluid from said second source to said shuttle valve.

11. In a gas turbine engine as described in claim 10, said operator movable means comprising an operator moved pedal pivotally connected to said fuel control means and operably engageable at times with said selectively operable means.

12. In a gas turbine engine as described in claim 11, said selectively operable means including selectively energized solenoid means connected to said regulating valve, switch means movable between open and closed positions for controlling energization of said solenoid 11 12 means to move said valve, said switch means being References Cited located adjacent said pedal and operativeiy engaged UNlTED STATES PATENTS thereby whereby movement of said pedal from an in- 3 181295 5/1965 Pauwels et a1 60 3916 operative position moves said switch means to effect an 5 3: 5/1966 Chadwick 6 energization of said solenoid means and a resultant movement of said regulating valve. JULIUS E. WEST, Primary Examiner. 

